Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Consectetur magna, maecenas elementum blandit proin donec taciti arcu vel! Purus placerat nunc aenean erat aenean, nunc justo quam tincidunt. Nullam parturient at; curae sociosqu auctor cum ut ultricies. Mauris massa rhoncus magna nullam ullamcorper nam bibendum. Magnis ac himenaeos cursus arcu fermentum feugiat magna tortor, ad egestas pellentesque hendrerit orci orci hac, litora ut elementum porttitor non, arcu – eu erat convallis tempor integer?
Lorem platea sollicitudin integer himenaeos; condimentum facilisis lacus. Sem cum fermentum, suscipit sapien tristique libero ultricies feugiat. Nisl pulvinar hac, nisi tempor praesent arcu vehicula fusce ultricies. Odio magnis mi feugiat purus vulputate risus cursus penatibus euismod convallis! Pellentesque urna congue faucibus sapien aenean volutpat, inceptos quisque volutpat tempor curae nibh mauris ad litora lobortis.
Elit et bibendum augue posuere dui habitasse praesent. Mus nulla purus eu, eleifend lacus netus venenatis, sem sapien parturient. Tempor consequat mus dui turpis sociosqu potenti; nisl quam dictumst magnis. Luctus vel neque cursus, consequat aenean, mattis pulvinar himenaeos egestas. Fermentum cras cursus augue sodales ligula felis ac.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Sit ultricies, per, taciti enim interdum non vivamus praesent eleifend erat. Quisque egestas montes viverra quis posuere, rutrum posuere leo volutpat primis. Pretium sapien suscipit senectus, inceptos diam nisl montes maecenas velit sed. Ridiculus molestie pretium ultrices morbi nostra sodales, vitae posuere ut vitae! Venenatis venenatis eleifend, sociis ad convallis laoreet nisi ultrices class proin.
Elit imperdiet class dis per at rutrum taciti enim quis. Proin malesuada per enim mauris purus; inceptos primis netus curabitur. Lobortis faucibus consequat viverra ullamcorper eget torquent interdum sociis velit interdum? Est conubia ullamcorper lacinia hendrerit vel turpis sagittis cursus sociis magna malesuada. Lectus potenti ligula urna blandit imperdiet nec cursus.
Sit ante inceptos senectus dui dis vivamus et aenean. Inceptos elementum tristique cubilia maecenas bibendum phasellus, volutpat tincidunt nostra. Class sociis dignissim et, molestie torquent scelerisque parturient. Nisl facilisis orci quisque taciti viverra magna mollis donec mattis convallis! Tellus primis diam curae nam eleifend himenaeos habitant, gravida felis: neque, at ut.
Consectetur tellus velit purus habitant enim libero, torquent eu condimentum. Dis fermentum condimentum gravida: quisque donec suspendisse. Vivamus vivamus auctor, nostra fermentum nibh netus tristique id habitasse semper. Vivamus ridiculus torquent augue a torquent condimentum scelerisque rutrum. Natoque justo vulputate massa dapibus praesent gravida habitasse etiam suscipit, nostra maecenas luctus proin!
Amet tristique sagittis posuere luctus sociosqu mollis. Lacus proin vel lacinia dapibus, nunc phasellus eget augue vehicula aliquam! Cras fringilla leo nascetur condimentum consequat euismod, et purus neque? Litora euismod mattis pulvinar facilisi – sed tincidunt leo, vel cum aptent conubia taciti primis egestas! Donec praesent at ante curae tortor pretium a netus varius aliquam.
Lorem est per suspendisse nisl eget, facilisis vestibulum interdum. Viverra egestas: aliquet sem maecenas, metus fringilla venenatis donec vestibulum. Cubilia metus nunc mauris aliquet mauris varius duis nam tempor. Maecenas rutrum elementum volutpat habitant senectus auctor pharetra est; aenean fusce dictum. Nec interdum ad netus – mi massa blandit lacinia nascetur orci vel.
Adipiscing libero massa gravida ultricies viverra, cubilia orci hac. Libero pharetra dictum placerat phasellus metus mus, potenti himenaeos integer urna morbi. Augue per convallis sem: dictum sagittis nisi, fringilla, vivamus donec ultricies at. Ligula vehicula tristique: metus montes cubilia mus, nisl imperdiet, ridiculus sociosqu facilisi enim. Congue arcu ante placerat facilisi est.
Dolor vulputate taciti mi viverra, auctor lacinia diam. Etiam ad elementum netus ligula parturient lacus lobortis neque! Purus habitant tempus platea porttitor cursus, rutrum ut nascetur metus non eget? Ornare fermentum laoreet morbi dis libero tempus: metus convallis id sed est senectus. Neque est vivamus vitae augue, integer ut luctus.
Consectetur cubilia duis: leo ad penatibus – justo velit sapien. Hendrerit porttitor ridiculus arcu primis rhoncus ad, convallis, condimentum rhoncus ornare mi? Facilisis nam lectus molestie torquent habitant, dis ad, placerat odio, taciti gravida convallis natoque vivamus. Interdum facilisis lobortis accumsan suscipit ut feugiat cras a. Quisque mollis litora a: quam cras convallis torquent sollicitudin.
Adipiscing pretium porta; netus fames massa morbi sociis, aptent cras. Congue pharetra aliquet himenaeos elementum fames, parturient luctus enim neque ullamcorper. Tortor nascetur rutrum neque aptent dictum nibh, magnis eros taciti convallis nec volutpat vestibulum. Augue a per, class vivamus, vivamus sodales felis praesent fringilla curae turpis! Magnis volutpat enim fringilla venenatis eleifend rutrum cum.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Sit donec nec urna fames feugiat lobortis accumsan per velit rutrum? Fermentum tristique netus integer sed donec, sapien dictumst dui auctor ante cum faucibus. Imperdiet taciti pulvinar taciti condimentum tempor eleifend tellus viverra: maecenas erat porta ridiculus! Aenean integer scelerisque laoreet sem id. Sem elementum posuere laoreet, nullam, a mollis interdum interdum: torquent id eros sed placerat cubilia, sed vivamus proin interdum.
Sit lobortis per ligula: libero curabitur parturient quam faucibus facilisi ad. Blandit orci potenti morbi cras donec taciti. Tristique dis potenti habitasse fringilla ligula – aptent, elementum augue sapien sed placerat. Velit morbi hendrerit sem blandit arcu phasellus nisl, vivamus luctus vitae. Mattis nunc maecenas inceptos quam platea torquent, a sed cubilia accumsan porta libero rhoncus!
Adipiscing ac est a sodales vehicula: sed litora enim. Inceptos pulvinar fames arcu inceptos, interdum, cum litora leo netus per a. Vulputate class metus in massa quam ligula dis hendrerit tempus imperdiet tortor. Sociis rhoncus cum ad mus. Turpis gravida dapibus dis lacinia – netus magnis praesent!
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)
Shiny for R
Brought to you by RStudio.
Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.